A vehicular seat element composed of a plurality of laminated different materials has been hitherto used as a seat for use in automobiles, etc. One example of such a seat element is a laminate composed of a cushion layer (pad) that is formed of a material having cushioning property and a substrate layer that is formed of a light-weight material and that has higher strength and rigidity as compared with the cushioning layer.
As the material from which the cushioning layer is formed, there is used, for example, a soft polyurethane foam that is configured to provide an occupant sitting thereon with good comfort and snug fit around the hip.
As the material from which the substrate layer is formed, on the other hand, there has been used, for example, a hard polyurethane foam. In recent years, however, a foam of a thermoplastic resin such as a styrene-based resin, an ethylene-based resin or a propylene-based resin has been used so that it has become possible to supplement the strength and rigidity of the cushioning layer and achieve weight reduction of the vehicular seat element. Thus, by laminating a cushioning layer of a soft polyurethane foam and a substrate layer of a thermoplastic resin foam together, it has become possible to obtain a vehicular seat element having composite properties.
As a method for producing such a vehicular seat element, there is a method using a mold. To be more specific, there is a method in which a previously prepared member (a thermoplastic resin foamed body) for forming a substrate layer is disposed in a mold cavity defined in a mold and in which a liquid raw material for forming a polyurethane foam is filled in the mold cavity in which the above member has been disposed, and is caused to foam to prepare a cushioning layer, thereby directly forming (laminating) the cushioning layer on a surface of the substrate layer.
However, because a cushioning layer formed of a polyurethane foam has poor adhesion property to a foamed body of a thermoplastic resin such as a propylene-based resin that forms a substrate layer, investigation is being made for suppressing the delamination between the polyurethane foam and the substrate layer. For example, Patent Document 1 proposes a method for producing a laminate in which that region of a surface of an expandable thermoplastic resin expanded beads foamed body which is to be contacted by a polyurethane foam layer, is heated at a temperature that is at least 80% of the softening temperature of the foamed body to soften and expand the expandable resin beads which constitute the contact region and to form undulations in the contact region. The polyurethane foam is then formed such that it enters into the recesses of the undulations.